Mangrove Forest

Mangrove
forest is a very important ecosystem.

Mangrove forest communities are one of the most interesting,
complex and important ecosystems on the Earth. Being muddy, smelly and
less attractive than sandy beaches, mangrove habitats were often
cleared before we started to understand their importance. Here is some
information about mangrove ecosystems, mangrove root systems, seeds,
destruction and conservation, and different species that are found in
Australia like red mangrove tree and others.

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What is a Mangrove Plant?
The most important characteristic of a mangrove plant is that it
tolerates salt water. Mangrove plants are not necessarily related to
each other. While many other plant groups consist of plants that are
evolutionary related, such as eucalypts,
acacias
or bottle
brush plants,
mangroves are any types of trees that tolerate salt water. The
interesting thing about them is that they don’t favour salt water, they
would grow in fresh water – if only they were better competitors. They
grow in the tidal salty waters because of the lack of competition from
other plants that are not able to tolerate such amounts of salt.

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Zoning in Mangrove Forest Communities
Mangroves
use different strategies to deal with salt. Some are able to exclude
salt from the intake by their roots, others have special salt glands
that excrete salt. Yet others exclude salt via their leaves. Because
different mangrove species are able to tolerate different amounts of
salt, mangrove communities tend to have a zoning of different species
parallel with the coastline.

Grey mangroves are usually found closest
to the water. Further away is a zone of red mangrove tree, and highest
up on the slope are yellow mangroves. These are the most salt-tolerant
species as highest tides bring the salt here, but it’s not rinsed out
as often as lower down towards the water. Higher up the slope behind
the mangrove zones are often saltmarsh and casuarinas.

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Red Mangrove Tree and Other Australian
Species
Mangrove forest communities are generally found along the northern
coasts of Australia. Grey Mangrove (Avicennia marina),
a species with leaves with grey underside, is the most common mangrove
in Australia. It is found along all the northern coasts, and as far
south as Shark
Bay in Western Australia; New
South Wales – Victoria border in eastern
Australia, and in a few pockets along the coasts of Victoria and South
Australia. River mangrove (Aegiceras
corniculatum) is another species that reaches quite far south
along
the coasts of Australia, but not quite to Victoria
and South Australia. Red Mangroves and
Black mangroves are more tropical species and restricted to further
north. Red mangroves (Rhizophora stylosa) are found
along the
whole coast of Queensland
and Northern Territory, and parts of the
coast of northern Western
Australia. Black Mangrove (Bruguiera
gymnorrhiza) is found along the eastern coast of Queensland,
and
the top end of Northern
Territory.

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Mangrove Roots
Because mangroves live on the coasts with tidal waters, they have to
have strategies to cope with the lack of oxygen to their roots in the
muddy ground that is often under water. Different species have
different ways to get their roots above the water level, at least at
the low tide.

Grey Mangrove has got special pneumatophores (below)
growing out of their roots and sticking out from the water. Red
mangrove tree has so-called stilt roots (above) that are high enough up
to be above the water level. Other species, like Looking-glass Mangrove
(Heritiera littoralis) has got buttress roots,
similar to
rainforest trees. Rainforest
trees have the buttress roots for the
same reason – the ground gets too wet when it rains a lot.

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Mangrove Seeds and Importance of Mangrove
Habitat
Mangroves also have clever strategies when it comes to seed dispersal.
Their seeds can float in the water and they can travel very far in the
water. Other species that reproduce and live in and around mangrove
ecosystems are mud crabs,
fish like barramundi,
oysters,
snakes,
crocodiles
and many shore birds but also terrestrial birds and animals. Mangroves
provide habitat, roosting and nesting sites for many shore birds, and
many migratory species. It is a very complex system where mangroves act
as nurseries for the young of many animals and support the whole
estuarine food web. In addition to that, mangroves act as a barrier
against storms, tropical cyclones (hurricanes) and flood
destruction; and they are an important filter of pollution like urban
or industrial runoff.

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Mangrove Forest Destruction and Conservation
Before we learned how complex and important the mangrove forest
ecosystems are, a lot of mangrove habitat was destroyed for mangrove
wood; and often it was cleared simply because they were muddy and
smelly areas, much better to turn into sandy beaches. As late as years
before the 2000 Sydney Olympics, parts of the Homebush mangrove
ecosystems were cleared because the space was needed for building the
Sydney Olympic Stadium. Other things that destroy intertidal wetlands
are oil spills; engineering works that increase siltation, removal of
freshwater flows and removal of inundation. A big part of mangrove
conservation is to transplant saltmarsh which is more vulnerable than
mangroves themselves, to maintain balance between the two.

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Note:
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correct in the language used in Australia.

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